This invention relates to a method and apparatus for feeding planar objects, such as cartons or panels. The invention is particularly suited for consecutively delivering paperboard cartons in a continuous motion-packaging machine to a downstream workstation of the machine.
Continuous motion packaging machines used to package articles such as beverage containers include numerous workstations, such as those which either manipulate a carton blank, group a selected numbers of articles or place the articles into fully formed cartons. Such packaging machines are well known, and typically include a carton feeder having a magazine which delivers carton blanks to a selecting device that continuously selects cartons one at a time from the magazine and delivers the selected cartons to a packaging machine conveyor. The magazine and the selecting device, or selector, collectively comprise the carton feeder, such as rotary feeders and segmented wheel feeders. The magazine delivers the cartons to the selector either by gravity or by way of a magazine conveyor, such as a chain conveyor, or by using a combination of gravity feed and a magazine conveyor. The packaging machine conveyor transports the selected carton to the next workstation, where the carton is manipulated in preparation for holding the articles.
Known selector assemblies may include reciprocating levers which position a vacuum cup to contact the front surface of the leading carton in the magazine, and pull at least a portion of that carton from the magazine, at which point it is engaged by a wheel for delivery to a conveying assembly, such as opposed nip rollers. These known systems are used in segmented wheel feeders, such as those disclosed in U.S. Pat. No. 4,034,658 to Sherman and U.S. Pat. No. 4,709,538 to Olsen, Jr. et al. Specifically, selector including a vacuum assembly and a picking assembly having a lever arm and supporting a vacuum cup to contact the leading carton or carton blank in the magazine. The top edge of the leading carton is pulled by the picking assembly below an upper retaining clip, and moved in a downstream direction. A rotating segmented wheel, that is a split-type wheel defining one or more cut out portions to form segments, turns toward the carton selection zone and the leading carton. The segments of the rotating wheel or wheels contact the carton, and cause the carton to move between the periphery of the segmented wheel and the periphery of an adjacent nip roller. Further rotation of the segmented wheel pulls the carton fully out of the magazine and downstream of the segmented wheel and nip roller to a further conveying device, such as additional nip rollers and/or belt or chain conveyors. The carton then is moved further downstream to the next carton workstation where the carton blank may be positioned for wrapping around a preformed bottle group or, in the case of a collapsed basket-type or sleeve-type carton blank, manipulated into an opened position for receiving the articles.
Packaging machine productivity commonly is measured by the number of fully packaged cartons containing a particular article group configuration processed through the machine per minute. Additionally, many packaging machines are capable of being configured to package different article configurations, which can increase or decrease the number of article groups packaged per minute. Other advances in the various workstations of packaging machines have increased the speed and efficiency at which the cartons are manipulated, the articles are arranged into groups and placed into the carton, and in fully enclosing certain types of cartons around the articles.
Increased or decreased packaging machine speed necessitates that components be operated faster or slower to match the speed change, which can require that some operations be initiated at different cycle positions. For example, it is known that vacuum valves controlling delivery of vacuum in feeders can be advanced or retarded to cause the vacuum delivery to reach the vacuum cup at the same feeder position, regardless of the carton feeder or carton opener speed. One known adjustable valve includes a disk with an arcuate slot contacting an adjacent disk with spaced ports. The rotational position of the slotted disk with respect to the ported disk can be changed selectively to alter the timing of the vacuum and pressurized air cycles. In another packaging machine operation, that is the carton closing workstation in certain types of packaging machines, the apparatus which delivers glue to a carton flap prior to folding mating flaps together can be controlled using a programmable limit switch/encoder assembly. As the encoder detects a change in machine speed, which can be a function of the position of a selected packaging machine component, the limit switch operates to control the timing of glue delivery to xe2x80x9cmatchxe2x80x9d machine speed.
As the packaging operations of the entire process increase in speed, the carton feeder also must deliver the cartons to the downstream workstations of the packaging machine at a matching rate. Known, high speed carton feeders can deliver certain types of cartons efficiently at rates up to approximately 300 cartons per minute, with the most common beverage container packaging machine speed presently operating in the range of approximately 150-300 cartons per minute. With increased machine speeds, however, problems can arise in carton feeding. As machine speeds approach 300 cartons per minute, the efficiency of known, high speed carton feeders decreases. For example, there is an increased risk of the picking assembly""s failing properly to remove a carton from the magazine, or failing to release the carton from the vacuum cups at the appropriate position. These occurrences can lead to additional problems, including machine jams and increased vacuum cup wear. Further, it is recognized that cartons which have become warped due to storage conditions but which are otherwise suitable for packaging articles are more difficult to remove from the magazine, especially at higher speeds. This difficulty also can exist particularly with respect to certain types of cartons, such as wrap-type cartons which include numerous performed design cuts and surfaces. Also cartons which have inconsistent varnish application tend to adhere to one another when loaded in the magazine, and can be difficult to select.
As known carton feeders have increased in speed, it has been found advantageous to use pressurized air to cause the carton to be efficiently released from the vacuum cups at the correct feeder position. The use of pressurized air in addition to the vacuum used to pull the carton from the magazine, especially at high machine speeds, presents additional challenges relating to delivering the vacuum to the vacuum cups at the precise moment the vacuum cups contact the carton, while also delivering pressurized air to the cups at the precise feeder position at which the cups must release the carton.
The present inventions include a method of feeding cartons or other planar objects, including but not limited to divider panels or partitions used in some beverage cartons, such as in an article packaging machine, and the apparatus for carrying out this method. The preferred embodiment of this apparatus includes a segmented wheel-type carton feeder capable of efficiently delivering carton blanks at rates of up to approximately 400-600 cartons per minute, under optimum conditions. The upper end of this range, however, presently is in excess of the efficient packaging capabilities of most known continuous motion, beverage container packaging machines. A first embodiment of the present invention includes an electronically actuated, solenoid dual valve assembly in which a valve for delivering pressurized air is coupled to a vacuum valve. This valve assembly itself is coupled to a distribution manifold which is placed in relatively close proximity to the vacuum cups. This arrangement optimizes valve efficiency by more accurately controlling the time required to deliver both the vacuum and the pressurized air to the cups at selected times or feeder positions. The inventions also can include a speed compensating assembly for the carton selector which advances or retards the valve assembly""s actuation in relation to the carton feeder speed. This speed compensating assembly can include an encoder driven from or reading the speed or position of one of the feeder shafts. The encoder is operatively connected to a programmable limit switch. The programmable limit switch (PLS) controls the operation of the valve assembly by signaling a valve controller based upon information manually programmed into the PLS and also upon data input into the PLS by the encoder. This speed compensation control can be necessary when operating the feeder at higher speeds, considering the rate at which the valves must be cycled, the time required for vacuum or air to reach the cups and the associated small margin of error acceptable in operating the valves at high feeder speeds.
In an alternative embodiment of the present invention, the packaging machine may utilize a specialized mechanical valve assembly for selectively applying a vacuum and compressed air (compression) to the vacuum cups. More specifically, the mechanical valve assembly is driven by the packaging machine and replaces the electronic solenoid-actuated dual valve. The valve assembly is formed from a relatively stationary, circumferentially adjustable valve base and a rotating port plate, each having surfaces which engage one another. The circumferentially adjustable valve base and rotating port plate work together to selectively provide a vacuum to the vacuum cup during the selection and transfer of a carton, and for providing compression to the vacuum cup to facilitate release of the carton. A circumferential adjustment of the valve base may advance or retard the successive application of a vacuum and compression applied to the vacuum cup.
In this alternative embodiment, the packaging machine includes an actuator for providing a radial adjustment to the vacuum valve base to advance or retard the vacuum and compression application timing in response to the machine speed. More specifically, the valve assembly includes a radial adjustment arm extending radially outward from the valve base. The actuator includes an air cylinder actuator assembly coupled between the packaging machine and the radial adjustment arm, wherein the cylinder linearly extends to rotate the radial adjustment arm on the valve base to adjust valve timing. In this embodiment, the controller may include an encoder that produces signal indicative of machine speed. A logic control unit receives the speed signal, determines the correct valve position for a given speed, and actuates a solenoid-actuated valve to extend or contract the air cylinder actuator assembly, which rotates the valve base plate, thereby advancing or retarding timing of vacuum and compression application to the vacuum cups.
The air cylinder actuator assembly may include first and second pneumatic cylinders connected in a tandem arrangement, wherein each cylinder has a retracted and an extended position. In this manner, when the cylinders are connected to form the assembly, the assembly may include a retracted position that includes the first and second cylinders in a retracted position, a first extended position with the first cylinder in an extended position and the second cylinder in a retracted position, and a second extended position wherein the first and second cylinders are both in an extended position. In this manner, the air cylinder assembly may adjust the valve assembly into one of three positions to advance or retard the timing of vacuum and compression application to the vacuum cup responsive to machine speed. Each valve position may correspond to a specific machine speed range or threshold speed.
The adjustable valve assembly includes an adjustable valve base plate that has a peripheral wall, an inner bearing surface, a vacuum supply inlet extending from the base plate peripheral surface and terminating at a first distance from the center portion of the valve assembly, a vacuum inlet port extending from the terminal end of the vacuum supply inlet and terminating at the base plate bearing surface, and a vacuum/compression outlet extending from the peripheral wall and terminating at a second distance from a center portion of the valve assembly. The adjustable valve base plate also includes a vacuum outlet port extending between the compression/vacuum outlet port and the base plate bearing surface at the first distance from the center portion of the valve assembly, and a compressed air outlet port extending from the compression/vacuum outlet port to the base plate bearing surface at the second distance from the valve assembly center portion. Finally, the adjustable valve base plate includes a compressed air inlet extending from the base plate peripheral surface and terminating at the second distance from the valve assembly center portion, and a compressed air inlet port extending between the compressed air inlet terminus and the base plate bearing surface.
The valve assembly also includes a rotating valve port plate, which also includes a bearing surface adapted to engage the valve base plate bearing surface. The rotating valve port plate includes an arcuate vacuum port having first and second ends. The arcuate vacuum port is disposed in the port plate bearing surface at the first radial distance from the valve assembly center portion. Finally, the valve port plate also includes an arcuate compressed air port in the port plate bearing surface, which is disposed at the second radial distance from the valve assembly center position. The valve base plate and rotating valve port plate bearing surfaces rotatingly engage one another. During a single rotation of the port plate, the arcuate vacuum port provides fluid communication between the vacuum inlet port and the vacuum outlet port of the base plate to provide a vacuum through the compression/vacuum outlet to the vacuum cup. As the port plate continues to rotate within a single revolution, the arcuate compression port provides fluid communication between the compressed air inlet port and the compressed air outlet port to provide compressed air to the vacuum cup through the compression/vacuum outlet after vacuum delivery is completed.
Circumferential position adjustment of the base plate in the opposite direction of port plate rotation advances vacuum timing so that the vacuum inlet port of the base plate intersects a leading edge of the vacuum air supply port of the rotating port plate earlier within a single carton acquisition cycle to compensate for increased machine speed. Circumferential position adjustment of the base plate in the direction of port plate rotation retards vacuum timing so that the vacuum inlet port of the base plate intersects a leading edge of the vacuum air supply port of the rotating port plate later within a single carton acquisition cycle to compensate for decreased machine speed.
Additional features which can contribute to the overall carton feeder efficiency include improvements to the magazine assembly which optimize carton delivery to the selector assembly. A carton metering device can be incorporated with the above inventions to deliver cartons to the selector in a controlled manner, which creates a gap or separation in the carton stream that results in reduced pressure by the carton stack on the leading carton, which is the carton being selected. Additionally, the increased efficiency at which the selector assembly operates permits the magazine to include additional or modified components that provide increased support to and alignment of the cartons, such as support blades and retaining clips which contact the leading carton over more surface area than in known magazines. These improvements enable the carton feeder to accommodate imperfectly formed cartons, such as bowed or warped cartons. These and other features of the present invention will become apparent upon reading the following specification, when taken in conjunction with the accompanying drawings.